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Abstract:

In one embodiment, an assembly includes a lift and a print bar mounted to
the lift. The lift includes first and second guide rods oriented parallel
to one another and perpendicular to an axis of the print bar across the
print zone. The first end of the print bar is slidably connected to the
first guide rod, the second end of the print bar is slidably connected to
the second guide rod, and the lift is configured to simultaneously move
both ends of the print bar along the guide rods. In another embodiment,
an assembly includes a chassis and a lift supported by the chassis. The
lift is configured to loosely hold a print bar and to raise and lower the
print bar over a print zone such that both ends of the print bar move
simultaneously.

Claims:

1. An assembly, comprising: a print bar having a first end and a second
end opposite the first end; and a lift including first and second guide
rods oriented parallel to one another and perpendicular to an axis of the
print bar across a print zone, the first end of the print bar slidably
connected to the first guide rod and the second end of the print bar
slidably connected to the second guide rod, and the lift configured to
simultaneously move both ends of the print bar along the guide rods.

2. The assembly of claim 1, wherein: the print bar axis is a horizontal
axis; the guide rods are oriented vertically; and the lift is configured
to simultaneously raise and lower both ends of the lift bar along the
guide rods while maintaining the printbar in a horizontal orientation
throughout the range of travel of the print bar up and down the guide
rods.

3. The assembly of claim 1, wherein the lift also includes a motor and a
transmission connecting the motor to the print bar for moving the print
bar along the guide rods.

4. The assembly of claim 3, wherein the transmission comprises: a first
rack connected to the first end of the print bar; a second rack connected
to the second end of the print bar; a single shaft operatively connected
to the motor, the shaft oriented parallel to the print bar axis and
extending between the first rack and the second rack; a first pinion on
the shaft for engaging the first rack; and a second pinion on the shaft
for engaging the second rack simultaneously with the first pinion
engaging the first rack.

5. The assembly of claim 4, wherein the lift also includes: a first
bracket slidable along the first guide rod, the first bracket carrying
the first rack and connecting the first end of the print bar to the first
guide rod; and a second bracket slidable along the second guide rod, the
second bracket carrying the second rack and connecting the second end of
the print bar to the second guide rod.

6. The assembly of claim 1, wherein: the lift also includes first and
second brackets each slidably mounted to a corresponding guide rod such
that the degree of motion of the brackets with respect to the guide rods
is constrained in theta X and theta Y; and the first end of the print bar
is connected to the first bracket at a first connection and the second
end of the print bar connected to the second bracket at a second
connection, the first end of the print bar unconstrained in theta Y at
the first connection and the second end of the print bar unconstrained in
theta X at the second connection.

7. The assembly of claim 6, further comprising a shaft operatively
connected to the brackets for simultaneously moving both ends of the
print bar, through the brackets, along the guide rods.

8. The assembly of claim 7, wherein the shaft comprises a single
rotatable but translationally stationary shaft carrying two pinions each
engaging a rack on a corresponding one of the brackets for simultaneously
moving both ends of the print bar along the guide rods through the
brackets.

9. The assembly of claim 8, further comprising: a chassis supporting the
guide rods and the shaft; a first stationary stop supported on the
chassis adjacent to the first end of the print bar; a second stationary
stop supported on the chassis adjacent to the second end of the print
bar; and the stops defining a limit in the range of travel of the print
bar along the guide rods corresponding to a print bar printing position.

10. The assembly of claim 9, wherein the stops constrain the print bar in
Z and theta Y when the print bar is in the printing position.

11. An assembly, comprising: a first guide rod; a second guide rod spaced
apart from and oriented parallel to the first guide rod; a first bracket
slidably mounted to the first guide rod and carrying a first rack; a
second bracket slidably mounted to the second guide rod and carrying a
second rack; a print bar having a first end connected to the first
bracket at a first connection and a second end connected to the second
bracket at a second connection; a single shaft carrying two pinions, each
pinion simultaneously engaging a corresponding one of the racks and each
pinion rotatable with the shaft; and a motor operatively couple to the
shaft for rotating the shaft.

12. The assembly of claim 11, further comprising: a chassis supporting
the guide rods and the shaft; a first stationary stop supported on the
chassis adjacent to the first end of the print bar; a second stationary
stop supported on the chassis adjacent to the second end of the print
bar; and the stops defining a limit in the range of travel of the print
bar along the guide rods corresponding to a print bar printing position.

13. The assembly of claim 12, wherein the stops constrain the print bar
in Z and theta Y when the print bar is in the printing position.

14. The assembly of claim 11, further comprising: a disk operatively
coupled to the shaft, the disk having markings or other indicators
thereon for determining a position, velocity, acceleration and/or other
characteristic of the disk; and a sensor operatively coupled to the disk
for sensing the indicators on the disk.

15. An assembly, comprising: a chassis; and a lift supported by the
chassis, the lift configured to loosely hold a print bar and to raise and
lower the print bar over a print zone such that both ends of the print
bar move simultaneously.

16. The assembly of claim 15, further comprising a print bar held loosely
in the lift.

17. The assembly of claim 16, wherein the print bar held loosely in the
lift comprises a first end of the print bar connected to the lift at a
first connection and a second end of the print bar connected to the lift
at a second connection and wherein the first end of the print bar is
unconstrained in theta Y at the first connection and the second end of
the print bar is unconstrained in theta X at the second connection.

Description:

BACKGROUND

[0001] In some inkjet printers, a media wide arrangement of stationary
printheads is used to print on paper or other print media moving past the
printheads. Unlike scanning printheads, there is no scan axis along which
these stationary page wide array (PWA) printheads may be moved to a
service station. Thus, another technique is needed to bring the PWA
printheads and the service station together.

DRAWINGS

[0002] FIG. 1 is a block diagram illustrating one example of an inkjet
printer in which embodiments of the new print bar lift may be
implemented.

[0003] FIGS. 2 and 3 are perspective views illustrating one example
embodiment of a print bar lift installed in a chassis. FIG. 2 shows a
print bar supported in the lift. The print bar is omitted from FIG. 3.

[0004] FIGS. 4 and 5 are perspective and side elevation views,
respectively, and

[0005] FIGS. 6 and 7 are elevation end views, illustrating the print bar
lift of FIGS. 2 and 3 in more detail.

[0006] FIGS. 5A and 5B are detail views taken from FIG. 5, FIG. 6A is a
detail view taken from FIG. 6, and FIG. 7A is a detail view taken from
FIG. 7 illustrating one example embodiment of the connection between the
print bar and the print bar lift shown in FIGS. 2-5.

[0007] FIGS. 8 and 9 are schematic end views illustrating one example
embodiment for the position of a print bar and print bar lift such as
that shown in FIGS. 2-5 installed in a printer.

[0008]FIG. 10 is a detail perspective view showing one example embodiment
for mounting the lift guide rods to the chassis.

[0010] FIGS. 12-13 are plan views showing one example embodiment for
mounting the lift brackets to the guide rods in the print bar lift of
FIGS. 2-5.

[0011] FIGS. 14-18 illustrate one example sequence of operation of the
print bar lift shown in FIGS. 2-5. FIGS. 14 and 16 show the lift in a
raised, servicing position and in a lowered, printing position,
respectively. FIGS. 15 and 17 show the lift in a raised, servicing
position and in a lowered, printing position, respectively, with an
optional spacer for a larger printhead to platen spacing. FIG. 18 is a
more detailed view showing the areas of contact between a stop and the
print bar.

[0012] The same part numbers are used to designate the same or similar
parts throughout the figures.

DESCRIPTION

[0013] Embodiments of the new print bar lift were developed to facilitate
servicing stationary PWA printheads. (Stationary in this context means
that the printheads and the print bar holding the printheads remain
stationary during printing.) In one example embodiment, the print bar is
constrained in the correct printing position but "floats" on loose
connections when raised to a servicing position, to reduce the risk of
binding on the lift guide rods even when using a lower cost, light duty
drive train. In one example embodiment, the lift is configured to
simultaneously move both ends of the print bar along the guide rods.
Embodiments of the new lift are not limited PWA printheads. The
embodiments shown in the figures and described below are non-limiting,
example embodiments. Other embodiments are possible and nothing in the
following description should be construed to limit the scope of the
disclosure, which is defined in the Claims that follow this Description.

[0014] Although embodiments of the new print bar lift are not necessarily
limited to printers dispensing ink or other liquids, and may be used for
devices dispensing other fluids, inkjet printheads generally are not
practical for dispensing fluids composed primarily of gas(es). Thus,
"liquid" as used in this document means a fluid not composed primarily of
a gas or gases.

[0015] A "printhead" as used in this document refers to that part of an
inkjet printer or other type of inkjet drop dispenser that expels drops
of liquid from one or more openings, including what is commonly referred
to as a printhead die, a printhead die assembly and/or a printhead die
carrier assembly. A "print bar" as used in this document means a
structure or device holding an arrangement of printheads that remains
stationary during printing. "Printhead" and "print bar" are not limited
to printing with ink but also include inkjet type dispensing of other
liquids and/or for uses other than printing.

[0016] In this document, "parallel" and "perpendicular" mean substantially
parallel and substantially perpendicular. Therefore, small misalignment
due to loose connections is included within the definition of each of
these terms.

[0017] The translational and rotational degrees of freedom of a print bar
and parts of a print bar lift are described with reference to X, Y and Z
axes, where the X axis extends in a direction laterally across a print
zone perpendicular to the direction the print media moves through the
print zone, the Y axis extends in a direction parallel to the direction
the print media moves through the print zone, and the Z axis is
perpendicular to the X and Y axes. Theta X refers to rotation about the X
axis, theta Y refers to rotation about the Y axis, and theta Z refers to
rotation about the Z axis.

[0018] FIG. 1 is a block diagram illustrating one example of an inkjet
printer in which embodiments of the new print bar lift may be
implemented. Referring to FIG. 1, an inkjet printer 10 includes a print
bar 12 spanning the width of a print media 14. Printer 10 also includes
flow regulators 16 associated with print bar 12, a media transport
mechanism 18, ink supplies 20, and an electronic printer controller 22.
Print bar 12 in FIG. 1 includes an arrangement of multiple printheads for
ejecting drops of ink on to a sheet or continuous web of paper or other
print media 14. Each printhead is electrically connected to printer
controller 22, typically through a flexible circuit tape holding multiple
electrical conductors. Each printhead is fluidically connected to one or
more ink supplies 20 through a typically complex ink flow path in print
bar 12 and through flow regulators 16. In operation, printer controller
22 selectively energizes ink ejector elements in a printhead, or group of
printheads, in the appropriate sequence to eject ink on to media 14 in a
pattern corresponding to the desired printed image. Controller 22 in FIG.
1 represents generally the programming, processor(s) and associated
memories, and the electronic circuitry and components needed to control
the operative elements of a printer 10.

[0019] FIGS. 2 and 3 are perspective views illustrating one example
embodiment of a print bar lift 24 mounted in a chassis 26. FIG. 2 shows a
print bar 12 supported in lift 24. Print bar 12 is omitted from FIG. 3 to
better illustrate other parts. FIGS. 4 and 5 are perspective and side
elevation views, respectively, and FIGS. 6 and 7 are elevation end views,
illustrating print bar lift 24 in more detail.

[0020] Referring first to FIGS. 2 and 3, chassis 26 represents generally a
stationary structure (relative to print bar 12) for supporting lift 24 in
a printer 10 (FIG. 1). In the embodiment shown, chassis 26 is constructed
as a sheet metal frame that includes side panels 28, 30 and struts 32,
34, 36 extending between side panels 28, 30. Chassis 26, for example, may
be part of a single integrated printer chassis or one component of a
multi-component printer chassis. Chassis 26 also supports a pair of
stationary stops 38 and 40 mounted opposite one another on side panels 28
and 30, respectively. As described in more detail below, print bar 12
lands on stops 38 and 40 to help properly position print bar 12 for
printing.

[0021] Referring now also to FIG. 4-7, lift 24 includes a pair of guide
rods 42, 44 and a corresponding pair of lift brackets 46, 48 that slide
along guide rods 42, 44. Each guide rod 42, 44 is mounted to a
corresponding side panel 28, 30 of chassis 26 as shown in FIGS. 2 and 3.
Mounting details for guide rods 42, 44 in chassis 26 are described below
with reference to FIG. 10. Print bar 12 is supported by lift brackets 46,
48 at each end 50, 52. Lift 24 also includes a motor 54 connected to each
lift bracket 46, 48 through a transmission 56. In the example embodiment
shown in FIGS. 2-7, transmission 56 includes a rack 58, 60 on each lift
bracket 46, 48, a pinion shaft 62 carrying pinions 64, 66 that
simultaneously engage racks 58, 60, respectively, and a drive train 68
coupled between motor 54 and pinion shaft 62. Drive train 68 represents
generally any suitable mechanism for transmitting the desired motive
force from motor 54 to shaft 62.

[0022] To reduce the risk of brackets 46, 48 binding on guide rods 42, 44
when raising and lowering print bar 12, while still allowing print bar 12
to be properly positioned for printing, print bar 12 is loosely connected
to lift brackets 46, 48 in some degrees of freedom but tightly connected
in other degrees of freedom. This mounting scheme allows for the vertical
translation of a page wide printbar 12 along guide rods 42, 44 without
precisely aligning rods 42, 44 in a parallel orientation. Binding and
over constraint conditions may be minimized by managing each degree of
freedom, X, Y, Z and theta X, theta Y, and theta Z even when using lower
cost, light duty lift and transmission components. Print bar 12, however,
must be constrained when print bar 12 is in the printing position for
proper printhead to media spacing and alignment. Stops 38 and 40 (FIGS.
2-4) affixed to chassis 26 (FIGS. 2 and 3) define the lower limit of
travel, and constrain print bar 12 in the correct printing position
parallel to and properly spaced from the print platen as shown in FIGS. 8
and 9.

[0023] One example embodiment for the print bar, lift bracket and guide
rod connections will now be described with reference to FIGS. 5-13. In
this embodiment, as detailed below, the connections between lift brackets
46, 48 and guide rods 42, 44 constrain each bracket 46, 48 in X, Y, theta
X and theta Y. Stops 38, 40 constrain print bar 12 in Z and theta Y (when
print bar 12 is lowered onto stops 38, 40). Thus, two systems are
competing to constrain print bar 12 in theta Y--rods 42, 44 acting
through brackets 46, 48 and stops 38, 40. Because theta Y is an important
print zone control, effecting ink drop flight distance (along with Z and
theta X), the more accurate vertical motion stops 38, 40 are used
exclusively to constrain theta Y. Consequently, the theta Y constraint
attempted by lift rods 42, 44 is neutralized by allowing each end of
print bar 12 to pivot in theta Y at the connection with lift brackets 46,
48. Similarly, the connections between rod 42, 44 and the corresponding
lift bracket 46, 48 are competing to constrain theta X. The theta X
constraint attempted by one of the rod/bracket connections 44/48 is
neutralized by allowing the lift bracket to pivot in theta X at the
connection with print bar 12.

[0024] Referring first to FIGS. 6, 6A and 8, print bar first end 50 is
constrained with respect to lift bracket 46 at a first lift bracket
connection 70 in Y, Z and theta X with two pins 72, 74 protruding from
print bar end 50 into mating holes 76, 78 in first lift bracket 46. The
use of two pin/holes 72/76 and 74/78 spaced apart in the Y direction
constrains print bar 12 in theta X. Each pin/hole connection 72/76, 74/78
constrains print bar 12 in Y and Z. In the example embodiment shown in
FIG. 6, round pins 72, 74 with flats fit into square holes 76, 78. Other
suitable pin/hole configurations may be used. Referring now to FIG. 5A,
print bar first end 50 is constrained in X by a rib 79 protruding from
bracket 46 and abutting print bar end 50. Rib 79 is narrow in Z to allow
print bar first end 50 freedom in theta Y. Ribs 79 spaced apart along Y
at each pin/hole connection also constrain print bar first end 50 in
theta Z.

[0025] Referring to FIGS. 7, 7A and 9, print bar second end 52 is
connected to second lift bracket 48 at a single pin connection 80. A pin
82 protruding from print bar second end 52 fits into a mating hole 84 in
second lift bracket 48. The single pin/hole connection 80 constrains
print bar second end 52 in Y and Z with respect to bracket 48 but allows
freedom in theta X. Referring to FIG. 5B, for second end connection 80, a
shortened rib 85 leaves a gap 87 between print bar second end 52 and
second lift bracket 48, allowing print bar second end 52 freedom in X.
The connections between rod 42, 44 and the corresponding lift bracket 46,
48 are competing to constrain X. The X constraint attempted by
rod/bracket connection 44/48 is neutralized by allowing print bar second
end 52 this freedom in X.

[0026] Print bar ends 50, 52 may be secured to lift brackets 46, 48 by
screws or other suitable fasteners at each pin/hole connection 72/76,
74/78 and 82/84. Screw holes are shown in the ends of pins 72 and 82 in
FIGS. 6A and 7A but screws are not shown in the figures to avoid
obscuring the alignment features at each connection.

[0028] Referring to FIG. 10, each guide rod 42, 44 is mounted to chassis
26 with a lower, rigid mounting tab 86, a spring tab 88, and an upper,
rigid mounting tab 89. The mounting for guide rod 42 is shown in FIG. 10.
The mounting for guide rod 44 on the opposite side of lift 24 is the same
as that shown for guide rod 42. In the example embodiment shown, mounting
tabs 86 and 89 are pressed out of a sheet metal chassis side panel 28. A
tapered lower end 90 of guide rod 42 fits into a hole 91 in rigid tab 86.
The upper end 92 of guide rod 42 snaps in under spring tab 88 to press
lower rod end 90 down into hole 91 in tab 86, constraining guide rod 42
in X, Y and Z. Although other suitable mounting configurations are
possible, the configuration shown allows for an easy and secure assembly
of guide rod 42 into chassis 26.

[0029]FIG. 11 is an elevation and partial section view showing the
connection between first lift bracket 46 and first guide rod 42. FIG. 12
is a plan view looking down on the top of lift bracket 46 on guide rod
42. FIG. 13 is a plan view looking up at the bottom of lift bracket 46 on
guide rod 42. The mounting of second lift bracket 48 on second guide rod
44 is the same as that shown in FIGS. 11-13. As shown in FIG. 12, a top
retainer part 94 of bracket 46 is beveled on one side in the Y direction
in a truncated V shape. As shown in FIG. 13, a bottom retainer part 96 of
bracket 46 is beveled on the other side in the Y direction in a truncated
V shape. The weight of print bar 12 and its cantilever positioning
extending out in the Y direction creates a torque on lift bracket 46 in
theta X that holds lift bracket 48 in contact with guide rod 44 at the V
shaped top 94 and at the V shaped bottom part 96, as shown in FIGS. 12
and 13 at contact arrows 98. That is to say, the weight and position of
print bar 12 automatically "preloads" guide rod 42 into the V shaped
retainer parts of bracket 46 to prevent lift bracket 46 from rocking back
and forth on guide rod 42 when print bar 12 is raised and lowered.
Clearances CX and CY between the inside dimension of lift
bracket 46 and outside dimension of guide rod 42 help reduce the risk of
bracket 46 binding on rod 42. The small bearing surface contact between
lift bracket 48 and guide rod 42 at these V shaped parts 94 and 96 allows
lift bracket 46 to move freely along guide rod 42. The bearing surfaces
may be lubricated to help ensure free movement.

[0030] One example sequence of operation of lift 24 will now be described
with reference to FIGS. 14-18. FIGS. 14 and 16 show lift bracket 46 in a
raised, servicing position and in a lowered, printing position,
respectively, with an optional spacer 100 retracted for smaller printhead
to platen spacing. FIGS. 15 and 17 show lift bracket 46 in a raised,
servicing position and in a lowered, printing position, respectively,
with spacer 100 extended for a larger printhead to platen spacing. Each
spacer 100 is mounted to a corresponding lift bracket 46, 48 such that it
can be extended into an operative position over stops 38, 40, as shown in
FIGS. 15 and 17, or retracted out of the way as shown in FIGS. 14 and 16.
Alternatively, each spacer 100 could be mounted to print bar 12. FIG. 18
is a more detailed view from the front of print bar 12 showing the areas
of contact between stop 38 and print bar first end 50 and spacer 100.
Although only once side of lift 24 is shown, both sides are raised and
lowered simultaneously through pinion shaft 62.

[0031] Referring to FIGS. 14 and 15, pinions 64 and 66 are driven
clockwise on shaft 62 to simultaneously raise print bar 12 connected at
each end 50, 52 to lift brackets 46, 48. Referring to FIGS. 16 and 17,
pinions 64 and 66 are driven counter-clockwise on shaft 62 to
simultaneously lower print bar 12. Referring now also to FIG. 18, at the
lower limit of travel shown in FIG. 16, with spacer 100 retracted, one or
more datum reference surfaces 102 on each end of the print bar 12 engage
mating datum reference surface(s) 104 on stops 38 and 40 to properly
position the print bar for printing at a smaller printhead to platen
spacing (PPS). The contact between datums 102 and 104 corresponding to
FIG. 16 is indicated by line 106 in FIG. 18. At the lower limit of travel
shown in FIG. 17, with spacer 100 extended, datum reference surface(s)
102 on each end of the print bar 12 engage mating datum reference
surface(s) 108 on spacer 100 to properly position the print bar for
printing, but at a larger printhead to platen spacing (PPS). The contact
between datums 102 and 104 corresponding to FIG. 17 is indicated by line
110 in FIG. 18. Spacer 100 may be a single thickness, as shown, for only
one PPS adjustment or spacer 100 may be stepped or wedge shaped to allow
for multiple PPS adjustments.

[0032] Referring again to the schematic end views of FIGS. 8 and 9, print
bar 12 in printer 10 includes printheads 112 spaced apart from a platen
114 carrying paper 14 or other print media at a desired PPS. The desired
PPS in FIGS. 8 and 9, for example, may be a smaller PPS (i.e., without a
spacer 100) or a larger PPS (i.e., with a spacer 100).

[0033] Referring again to FIGS. 4 and 5, in the example embodiment shown,
an encoder 116 is used to help control lift 24. Encoder 116, for example,
includes an encoder disk 118 that rotates with shaft 62 and a sensor 120
that senses markings or other indicia on disk 118. The data/signals from
sensor 120 indicate characteristics of disk 118 such as position, speed
and acceleration and, accordingly, the corresponding characteristics of
print bar 12. This information may be used by printer controller 22 (FIG.
1) to control motor 54 to move print bar 12 to a desired position at a
desired speed and acceleration. For example, it may be desirable when
raising and lowering print bar 12 to accelerate and decelerate lift 24
slowly to avoid rocking lift brackets 46, 48 on rods 42, 44 (by
overcoming the guide rod preload described above). For another example,
information from encoder 116 allows controller 22 (FIG. 1) to accurately
position print bar 12 at any location along its full range of travel on
lift 24.

[0034] As noted above, the example embodiments shown in the Figures and
described above do not limit the disclosure. Other embodiments are
possible. For example, although guide rods 42, 44 are shown as having a
round cross-section, they may be rectangular or any other suitable shape.
Also, guide rods 42, 44 need not be vertical. While it is expected that
guides rods 42, 44 will usually be oriented vertical and perpendicular to
the long axis of print bar 12, rods 42, 44 may be disposed at other
orientations. Accordingly, these and other forms, details and embodiments
may be made without departing from the spirit and scope of the
disclosure, which is defined in the following claims.

Patent applications by Dan Dowell, Albany, OR US

Patent applications by Jeffrey T. Hendricks, Camas, WA US

Patent applications by Joseph E. Scheffelin, Poway, CA US

Patent applications in class With means to scan fluid ejector relative to the receiving medium

Patent applications in all subclasses With means to scan fluid ejector relative to the receiving medium